But as far as marriott competing against itself...
Can you check this link:
https://www.marriott.com/hotel-prices/faqs.mi
Under:
What information do I need to send to Marriott to help verify my claim?
"The claim form outlines all required information for your claim. You will need to provide Marriott with specific information depending on where you found the comparison rate to help us verify your claim......
If your comparison rate was found on a
Marriott Internet Web site, through Marriott Worldwide Reservations, at a Marriott hotel, or through a travel agency or travel management company, your claim must include a Marriott confirmation number."